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Holographic lens and liquid crystal image source for head-up display

  • US 3,915,548 A
  • Filed: 11/29/1974
  • Issued: 10/28/1975
  • Est. Priority Date: 04/30/1973
  • Status: Expired due to Term
First Claim
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1. In an aircraft, a head-up display system for use in displaying an image for viewing by a pilot in the pilot'"'"''"'"'s field of view while looking out of the aircraft at a scene in a forward direction, comprising in combination:

  • an aircraft canopy integral with the aircraft;

    a holographic lens comprising an optically transparent substrate having photoresponsive material having as an integral portion thereof a plurality of holographic elements in a side-by-side abutting arrangement for collimating light from a focal plane, and having a known operating bandwidth of light of preselected wavelengths, said lens being disposed in said aircraft in the field of view for collimating light directed to the pilot from all points of a light image produced in the focal plane and simultaneously combining the image light thus collimated and directed to the pilot with light from said scene whereby said pilot sees said image as if emanating from a source in said field of view at infinity, said holographic lens being disposed on the inside surface of said canopy;

    a relay lens; and

    means optically coupled to the holographic lens for producing said light image at said focal plane, said image having a peak band of wavelengths within the operating bandwidth of said holographic lens, and wherein said means for producing said light image at said focal plane is comprised of;

    an array of liquid crystal cells disposed in rows and columns in an image source plane, said relay lens projecting said image source plane to said focal plane, each cell of said array of liquid crystal cells comprising conductive plates parallel to said focal plane and a layer of liquid crystal material sandwiched in the mesophase state;

    an array of horizontal and vertical transparent conductors, each one of said horizontal conductors being connected to all cell plates on one side of said array of cells of a distinct one of said rows of cells, and each one of said vertical conductors being connected to all cell plates on another side of said array of cells of a distinct one of said columns of cells;

    means electrically connected to said transparent conductors, for selectively energizing said distinct one of each of the rows and columns of the conductors energized at one time to establish an electric field across said layer of liquid crystal between the plates of a single cell; and

    a light source so disposed as to illuminate said holographic lens through said array of cells and said relay lens, said source emitting light having said peak band of wavelengths, whereby light incident on said holographic lens is modulated at different points to produce said light image as a function of electric fields established across said cells.

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